I have a question about cropping pictures to standard picture/canvas sizes. I do paintings and want to make prints available. I took pictures of paintings with hi-res camera. The problem I have is cropping the image to match the size of the canvas or at least a proportionally smaller size, without messing ratio aspect. example- if canvas in picture is 16x20, how can I crop it so I can print it 16x20 in a 17x22 paper? If I have several different pics of different paintings, how do I crop so all print out the same size?